1. Field of the Invention
The present invention relates to a diagnosis apparatus and a method thereof for a control system having a plurality of sensors in a steel plant, an electric power plant, a general industry and so on, particularly to a diagnosis apparatus and a method thereof preferable to determining degraded sensors of which the measurement accuracy is growing worse due to aged deterioration, indicating apparent normal indication of each sensor.
2. Description of the Related Art
One of conventional sensor diagnosis methods is a diagnosis method of detecting a degraded sensor by using the indicative magnitude relation naturally existing among sensors as described in "Diagnosis by Using An Immune Network Information Model (in Japanese)", by Ishida, Proc. of A Symposium on The Third Autonomous Distributed System, January, 1992. Further, as described in Japanese Patent Application Laid-Open No.35329/1993, another conventional sensor diagnosis method is a method of detecting a degraded sensor by comparing an output signal of the sensor with the predetermined functional relation among output signals from sensors.
The above-mentioned conventional methods have the following problem. That is, although a degraded sensor can be easily detected by the methods if an object control system is so simple that the indicative magnitude relation or the functional relation among output signals from sensors is clearly determined, the methods is not applicable in a case where the indicative magnitude relation or the functional relation are complicated and hardly extracted.